Pen arm lifter



1935 I R. H. MOPHERSON ET'AL 2,022,366

PEN ARM LIFTE R Filed Ocfc. 16, 1934 2 SheetsSheet l INVENTORS. Re barf ll M Phu-a Loci/S C. Cam'ssl'ml' ATTORNEYS,

Dec. 3, 1935. R. H MOPHERSON ET AL ,022,866

PEN ARM LIFTER Filed Oct. 16, 1954 2 Sheets-Sheet 2 INVENTORS- R'Obtr'f' Aauis C Carwo1m BY Patented Dec. 3, 1935 UNITED STATES PATENT OFFICE PEN ARM LIFTER Application October 16, 1934, Serial No. 748,440

7 Claims.

This invention relates to improvements in lifting devices commonly employed to raise the pen arm of recording instruments off a chart when the door of the instrument housing is open.

One important object of this invention is to provide an automatically operated pen arm lifter for recording instruments and the like which reduces to .a minimum and substantially eliminates vibration of the pen arm when engaged thereby.

Another important object of this invention is to provide an automatic pen arm lifter for recording instruments which is retracted so as not to be visible through the window of the instrument casing when not in use.

A further object of this invention is to provide a pen arm lifter capable of the above operations which is automatically operated by the opening and closing of the door of the instrument casing.

These and many other objects as will appear from the following detailed description are secured by means of this invention.

This invention resides substantially in the combination, construction, arrangement and relative location of parts, all as will be described is complete detail below.

In the drawings,

.Figure 1 is a front view of a recording instrument with some parts broken away inconnection with which this invention is illustrated;

Figure 2 is a topplan view of one form of the pen arm lifter;

Figure .3 is a vertical, central, cross-sectional view of a modified form of, pen arm lifting device;

Figure 4 is a cross-sectional view taken on the line 4-4 of :Figure 1 with the cover removed;

Figure 5 is a similar view showing the cover inplace or closed;

Figure 6 is a top plan view of a modified form of pen arm lifter;

Figure '7 is a side elevational view of this modified form; and

Figure 8 is a vertical, central, cross-sectional view thereof.

This invention is concerned with pen arm lifters, such as are used with recording instruments of the type in which a pen or stylus attached to the free end of a pivot arm draws or inscribes a record on a circular chart which is rotated by means of a clock or motor; or which ismade to rotate at some fixed or variable angular velocity proportional to the motion of some other mechanism; or which is made to rotatev in accordance with some fixed schedule. The chart is commonly printed. with lines representing time intervals and usually is provided with spaced lines concentric with its axis of rotation, which lines represent the magnitude of changes to be recorded, such aschanges in pressure, flow, temperature and the like. The pen arm which car- 5 ries the pen or stylus has the end opposite to that supporting the pen or stylus attached to a shaft which is caused to rotate or oscillate in proportion to changes in the recorded quantity. The construction and mode of operation of such 10 recorders are weli known in a number of forms.

The pen arm itself usually is made from a thin fiat strip of spring metal. The slight initial spring tension of the arm and the weight of the pen at its free end tends to hold the pen point L5 against the paper chart with a light uniform pressure, thus ensuring a smooth inked line with the minimum of drag between the pen and the chart. The chart itself is commonly supported upon a stationary chart plate through a hole in 20 the center of which the driving shaft from the clock or motor extends and upon which the chart is clamped. Thus as the clock or motor rotates the chart rotates with it.

The :pen arm is swung back and forth over the 25 chart about its pivot point by and in accordance with changes in the conditions to be recorded, thereby inscribing upon the chart a record of these variations as a function of time.

When it is necessary to remove or change the chart it is desirable that the pen arm be lifted and held away from the chart. To accomplish the liftingpf the pen it is customary to provide a pen arm lifter which usually consists of a movable shaft or plunger mounted upon its axis normal to the-plane of the chart and carrying an extended arm projecting from the plunger toward the center of the chart. This arm is approximately parallel to the plane of the chartand the plunger is so positioned that the arm lies under the pen arm for all normal positions thereof. When the pen is inscribing a record on the chart the lifting arm is depressed away from the pen arm and towards the chart.

When the door of the instrument casing is opened for the purpose of removing or changing the chart the plunger carrying the pen arm lifter is raised, carrying withit the lifter arm, which in turn picks up the;pen arm and lifts the pen clear of the chart. In some forms of instrument the raising and lowering of the lifter arm is accomplished manually or as noted above may be operated automatically by the act of opening or closingthe door of the casing. In some cases the lifting arm is raised manually but is depressed by 55 the instrument door as it is closed. The devices in the forms now known to applicants are unsatisfactory.

The pen arm as stated above is quite flexible and being of considerable length and supported from one end only is inherently subject to vibration, which tendency is increased by the added weight of the pen at the end thereof. If the pen arm is suddenly lifted, by means of the pen arm lifter, the pen arm and pen will vibrate rapidly in a plane normal to the chart. The vibration of the pen arm upon lifting is very objectionable, as it splatters and throws ink over the chart and quite often over the operator who is changing the chart. Another disadvantage of known pen arm lifters is found in the fact that they at all times project out across the chart in an unsightly manner, which is undesirable under present practice where the trend is towards improving the appearance and design of such instruments.

The present invention is of such form that it reduces or prevents vibration of the pen arm while it is being lifted from the chart and is automatically moved out of view when the door of the housing is closed.

The structure by means of which these objects and advantages are secured will now be described in detail.

The invention is illustrated in several forms in the drawings and as applied to a recording instrument. The instrument comprises a casing I having a cover 2 supporting a glass window 2' and pivotally attached to the casing by the hinges 3. At this point it may be noted that the cover may merely frictionally engage the casing without the use of hinges within the scope of this invention. At 4 is the usual pen arm pivotally mounted at 5 on a plate 6 secured to the casing in accordance with well known practice in the art. The'pen arm rotates in a horizontal plane over the horizontally mounted chart. The pen itself is illustrated at "I attached to the end of the pen arm so as to engage the chart 8 which rests upon the fixed chart plate 9. At I2 is the motor which causes rotation of the chart. The chart is attached to the motor spindle III by means of a clamping nut I I in accordance with well known practice.

The pen arm lifter rod is shown at I 3 attached to a plunger I4 which is mounted to slide in a vertical direction at right angles to the plane of the chart. The plunger I4 is mounted, as illustrated in Figures 1, 4 and 5, inclusive, in a tubular housing I5. The plunger I4 is provided with a shoulder formed by a reduction in diameter of the plunger which engages one end of a light spring I6 mounted in the housing and surrounding the plunger. At I! is a short pin mounted on the plunger I4 and engaging with a slot I8. This slot I8 is the same in all three forms of the device illustrated, and is only shown in detail in Figure '7. This slot has two vertical portions connected by an inclined portion so as to cause oscillation of the plunger and the attached lifter rod or rods as the plunger moves in a vertical plane. The

housing is provided with a threaded plate 2| by means of which it may be attached to the undersurface of the chart plate. As shown in Figure 5, the cover is provided with an arm or projection I9 for engaging the extended end of the plunger as the cover is closed or put in place to depress the plunger.

In Figures 1 and 4 the parts are shown in the position with the door open and the pen arm lifter engaging the pen arm to hold it away from dotted lines in Figure 1.

the chart. When the door is moved to a position to engagethe top of plunger I4 at the bracket I9 the plunger begins to move downwardly without rotation for a distance determined by the upper vertical end of the slot IS. The length of this 5 portion of the slot is proportioned so that for the first movement of the plunger and the arm I3 there is no rotation and the pen arm is permitted to move downwardly only.

Further movement of the door towards the 10 closed position depresses the plunger so that the pin ll moves into the inclined portion of the slot I8. This inclined portion is in the form of a helix or thread so that continued downward movement of the plunger causes rotation thereof. 15 At such an intermediate position the arm I3 is moving towards the casing, as illustrated by When the pin Il reaches the lower vertical portion of slot I8 the arm I3 is over against the casing, as illustrated in dotted 20 lines in Figure 1, and the final closing movement of the cover and depression of plunger I4 occurs in a vertical direction to move the arm I3 down into contact with or close to the chart plate at the edge. 25

On reverse movement, that is with the cover of the instrument moving towards open position, the plunger I4 and arm I3 move upwardly under the action of spring I6, first in a vertical direction and then with a combined vertical and r0 30 tational movement which causes the arm I3 to first engage the under-surface of the pen arm near the pivot point 5, as will be clear in Figure l. The lifting arm I3 first strikes the pen arm, say at a point indicated by the right hand dotted outline of the lifting arm I3 to which it moves from the left hand dotted position against the casing. This first impact will have a tendency to start the light spring pen arm vibrating but as the lifting arm continues to swing towards the 4 v free end of the pen arm the period of vibration of the spring arm will change, thus dampening out the vibrations set up immediately before. The tendency of the pen arm to vibrate is less severe with a combined rotational and lifting 45 movement than would be the case where the lifting arm merely moves in a vertical plane. The net result of these operations is that the pen arm, although it may be lifted quickly, is lifted smoothly and with very little vibration. It will 50 be noted that the lifter arm I3 is at all times parallel to the chart.

The form of pen arm lifting device illustrated inFigure 3 is substantially the same as that illustrated in Figures 1, 4, and 5, with the exception 55 of the relative arrangement of parts. In the form illustrated in Figure 3 the plunger I4 is of uniform diameter throughout its length with the exception of the collar 20 intermediate its length against which one end of the spring I6 rests. 60 In this case the slot I8 instead of being placed near the center of thecasing I5 is placed at one end. The shape of. this slot I8 is as previously stated the same as the shape of the slot illustrated in the bracket form of device shown in Figures 65 7 and 8. It will be seen that the arrangement of Figure 3 is the full equivalent of the arrangement of Figures 1, 4, and 5 varying only in minor details of construction and relative positioning of the parts. 70

The modified construction of Figures 6, 7, and 8 shows instead of the tubular housing I5 of the other figures a U-shaped plate or bracket I5, in the ends of which the plunger isslidably mounted, and in which the slot I8 is formed as before 75 for engagement by the pin II. In this form of the device a pair of lifter arms l3 are shown. This is to illustrate the fact that the invention may be applied to recording instruments having two or more independent pen arms as are frequently employed today.

From the above description, the two important advantages of the invention are apparent. The tendency of the pen arm to vibrate when engaged by the lifter arm is counter-acted and the lifter arm is moved back so as not to be visible through the window of the instrument casing when the cover for the casing is in closed position.

From the above description it will be apparent that this invention resides in certain principles of construction and operation which may be embodied in other physical forms Without departure from the scope thereof. We do not, therefore, desire to be strictly limited to the disclosure as given for purposes of illustration but rather to the scope of the appended claims.

What we desire to secure by Letters Patent is:

1. In a recording instrument the combination of a casing having a movable cover, a pen arm pivotally mounted within the casing, a lifter arm, and means mounted on the casing and positioned to be operated by the cover as it is moved to closed or open position for moving the lifter arm from engagement with the pen arm and towards the wall of the instrument housing or from the wall of the instrument housing and into engagement with the pen arm respectively.

2. In a recording instrument employing a chart, the combination comprising a casing, a cover for said casing, a pen arm for engaging the chart, and means operated by opening and closing the cover of the casing for progressively engaging the pen arm from one end towards the other and simultaneously raising or lowering it.

3. In a recording instrument as described, the combination comprising a casing having a cover, a pen arm movably mounted within the casing, a plunger mounted in the casing, means mounted on the cover for engagement with the plunger, a lifter arm mounted on said plunger, and means for causing rotation of the plunger simultaneously with vertical movement thereof.

4. In a recording instrument as described, the combination comprising a casing having a cover, a pen arm movably mounted within the casing, a plunger mounted in the casing, means mounted on the cover for engagement with the plunger, a lifter arm mounted on said plunger, and means for causing the plunger to have vertical movement near each end. of its stroke and combined vertical and rotational movement intermediate the ends of its stroke.

5. In a recording instrument as described, the combination comprising a casing having a cover, a pen arm movably mounted within the casing, a plunger mounted in the casing, means mounted on the cover for engagement with the plunger, a lifter arm mounted on said plunger, a support for said plunger having a slot therein and a pin on said plunger engaging said slot whereby movement of the plunger as the cover is closed occurs both vertically and rotationally.

6. In a recording instrument the combination of a casing having a movable cover, a pen arm pivotally mounted within the casing, and a lifter arm pivotally mounted to swing on an axis parallel to the pivot axis of the pen arm and means cooperating with the cover for moving the lifter arm into and out of engagement with the pen arm and for swinging the lifer arm on its axis.

'7. In a recording instrument employing a chart, the combination comprising a casing have a removable cover, a pen arm pivotally mounted within the casing, a lifter arm for engaging the pen arm to move it away from the chart when the cover is removed and means cooperating with the cover for causing combined linear and rotational movement of the lifter arm as the cover is applied and removed.

ROBERT H. MoPHERSON. LOUIS C. CARISSIMI. 

